Automatic mechanical return device



Dec. 10, 1940. R LARAQUE 2,224,481

AUTOMATIC MECHANICAL RETURN DEVICE Filed March 17. 1939 3 Sheets-Sheet l v mvsuroz, Rom/v0 LARnQuE,

BY ATTORNEY,

Dec. 10, 1940. v R. LARAQUE 2,224,481

AUTOMATIC MECHANICAL RETURN DEVICE Fil'ed March 17, 1939 3 Sheets-Sheet 2 r Q 27 2s a 14 J/ g Q '47 J 15 INVENTOR- ATTOR EY 20mm) L HQUE\ Dec. 10, 1940.

R. LARAQUE AUTOMAT I C MECHANICAL RETURN DEVI CE 3 Sheets-Sheet 3 Filed March 17, 1 939 INVENTOBJ Rom/v0 Remus. My

' ATTORNEY,

Patented Dec. 10, 1940 UNI-TED r STATES 2,224,481 AUTOMATIC MECHANICAL RETURN DEVICE Roland Laraque, Paris, France Application March 17, 1939, Serial No. 262,510

' In Luxemburg March 18, 1938 3 Claims.

The present invention has for its object a. mechanical return device to a given position of. P11 parts capable of performing evolutions within a certain limit, about an axis of rotation such as trap doors, panels or other material of all kinds.

The invention is more particularly suitable in the case where the device is to serve as a strut, ay or counter-brace or similar organ. Thus it. can for instance be applied for returning the re- *racted landing gear of aircraft to the lowered position where the device has the advantage over ther systems of necessitating no supplementary fixing accessories.

A feature of the device resides in that'it comnr ses two elements articulated to one another n known manner and on one of which is arranged a powerful resilient system (with springs or pneumatic or hydropneumatic) acting on a pusher provided with rollers and which bears on a cam carried by the second element and of a shape such that it tensions the spring from the start of the folding of the one element on the other and that it serves as the point'of application of the force accumulated by the spring at the extensionof the elements which force must ensure the energeticreturn of these latter to their position of alignment.

The characteristics of this device will moreover be brought out during the course of the follow.- ing description and with reference to the accompanying drawings which relate to means for automatic keeping in position of an aircraft landing gear.

The drawings show by way of example:

Fig. 1, means for lifting and keeping in position the landing gear of an aircraft;

Fig. 2, the working diagram of a liftingjac for the said landing gear;

Fig. 3, the return device shown in longitudinal section;

Fig. 4, a section taken on the line 4-4 of Fig. 3.

It is known that a landing gear generally consists of two half gears each comprising a fork, a lifting device and a stiffening device.

The fork comprises two resilient-limbs I (Fig. 1) terminated by a bearing 2 in which is mounted the axis of the wheel 3. Each half gear is'articulated on an axle 4 carried by the motor spindle of the aircraft.

The raising of the half gear is ensured by one or more jacks 5 articulated on the one hand at 6 on the said driving axle and on the other hand at I on the front bar 8 of the stiffening or bracing 5; device.

This bar 8 is itself articulated at 9 on the driving axle and at Ill on the rear bar II which is articulated to the half gear at l2, for example.

With a landing gea'rmounted in this manner .the work of each jack 5 can be representedby the 1 diagram shown in Fig. 2.

On this latter, the load proper due: to the weight applied to the spindle of the jack is shown by the curve I and the load due to the: wind by the curve II.

The curve III represents the resultant; of the weight and the wind (in the case where: their effects add together). a

It will immediately be seen that part-off the force set up in the jack remains unutilised at the start of the course of the movable equipmentthereof.

If one then uses the device made in accordance with the invention this force can be utilised for setting a resilient system adapted to ensure a. strong return action of the bars 8 and It to alignment.

In one form of construction given by way of simple example,'the particular fitting of system for maintaining the gear in position is effected as follows:

The bar at the front is formed of a tubular body 8 (Fig. 3 and 4) terminated at its upper extremity by an articulation shackle on the driving axle and, at its lower extremity, by a second shackle l3 through which passes the articulation axis ID of the rear bar ll.

On the axis Ill can pivot the said rear bar which is provided, for this purpose, with a shackle l4 embracing a cam l5 securedboth by the axle l0 and by a pin l6.

On the cam l5 rests, through the intermediary of a roller ll, a pusher 18' consisting of two limbs passing through the end IQ of the tubular body 8 of the front bar.

In the bottom or end I8 is screwed a rod l9 surrounded by a tube 20 which bears on the end and which passes through a sleeve 2| integral with the limbs of the pusher l8.

The tube 20 serves as guiding member for washers 22 of the type known by the name of Belleville held piled together under tension against the sleeve 2| by a cap 23 the position of which may be regulated by a nut 24 screwing on rod l9, and permits of modifying the pressure exerted by the washers on the said sleeve.

It will immediately be seen that the latter can slide in the tube 8 in relation to the end l9 which limits its travel towards the articulation III.

This rotation is rendered possible by the hinge H} which allows the stiifening or bracing system to fold as is shown in dot and dash lines in Fig. 1. This done the cam l5 pushes back the pusher i8 and the sleeve 2| which compresses the washers 22 against the cap 23.

This compression takes efiect at the commence- I ment of the folding or raising action of the stiifening system and absorbs'power, in the working of the jack 5, which can be represented by the curve IV of the diagram in Figure 2.

Henceforth it will be seen from an examination of this diagram that the resultant. load: weight of the gear, wind and return movement of the mechanism, can be depicted by the curve V which represents a much more rational use of the power set up and consequently, corresponds to a better efficiency thanthatrepre sented by the curve III. a

It follows that without use of supplementary air, the device described hereinbefore permits of storing, by reason of the setting of the spring formed by the washers 22, a force utilizable at the lowering of the gear. It will be seen in fact that the spring set from the start of the raising of the gear isjheld so for the remainder of the course of the cam I5 starting at the point IS, without requiring from the jack any effort other than the very small amount required to overcome the friction of the roller l1 and of the axle Ill.

At the lowering oi! the gear it is unnecessary for the major part of the course, to use any source of power other than that provided by the gear and in case of need, the effort exerted by the wind on the latter. But especially at the end of,

the course, the influence of the weight diminishes and it is at this moment that the taut'ened spring acts on the cam 15 to cause the energetic alignment of the two bars of the bracing system, the return efiort being, for instance, maximum when the alignment is effected.

This last feature therefore presents all the advantages of ensuring, with a suitable adjustment of the bracing system to causea slight break in alignment towards the base, safety in landing in the case where the locking action or holding ensured by the jack should accidently have become insumcient.

It is obvious that modifications in shape and Nevertheless said washers can be replaced by washers of rubber, insulated or notirom each other by metal washers or by coil springs or by reinforced rubber washers or even by a pneumatic or hydro-pneumatic arrangement.

What I claim is:

1. In aircraft having a fuselage and a forked landing gear; comprising a tubular member articulated to said fuselage, a rod member articulated to the fork of said landing gear, an axle, said tubular member and said rod member being pivoted about said axle, cam means mounted on said axle and fixed to said rod member to swing therewith about said axle, a plunger including an element bearing against saidcam means, said plunger extending within and being slidably 0perable relatively to said tubular member, and resilient means within said tubular member urging said plunger against said cam means, whereby upon .retraction of said landing gear said tubular member and said rod member are positioned out-of-alinement and upon expansion of said resilient means said tubular-member and said rod member are brought into alinement.

2. In an aircraft having a fuselage and aforked landing'gear; comprising a tubular member articulated to said fuse1age,- a rod member articulated to the fork of said landing gear, an axle, said tubular member and said rod member being pivoted about said axle, cam means mounted on said axle and fixed to said rod member to swing therewith about said axle, a plunger including :an element bearing against said cam means, said plunger extending within and being slidably operable relatively to said tubular member,-resi lient means within said tubular memher, and means for regulating said resilient means and forming an abutment therefor, said resilient means urging said plunger against said cam means, whereby upon retraction of said landing gear said tubular member and said rod member are positioned out-of-alinement and upon expansion of said resilient means said tubular member and said rod member are brought into alinement. v

3. 'In aircraft, as claimed in claim 1-, said re- 

